Microsoft Gets Philosophical About IE 9 Chakra Pains

The Microsoft Internet Explorer team on Wednesday described some of the decisions being made to accommodate the ECMAScript 5 spec in Internet Explorer 9.

ECMAScript is more popularly known as "JavaScript," and IE 9 will feature a new Microsoft JavaScript engine called "Chakra." Possibly, the Chakra engine is named after the ancient Hindu concept of chakras, or the seven major body energy centers. If so, it seems that Microsoft has been experiencing some "subtle body" pains in trying to cram ECMAScript into its Chakra engine.

It turns out that the ECMAScript 5 spec is not always clear and may ignore some conventional Web coding practices, according to Microsoft. In reaction, Microsoft's IE team has resorted to "principled decision making" to sort out the mess, an IE blog post explained.

The blog noted four examples where Microsoft may veer from ECMAScript 5 spec in IE 9. One issue is the accommodation of regular expression literals, such as the "]" symbol. Another concerns the use of underscore characters to indicate experimental methods (such as "__defineGetter__" and "__defineSetter__"). A third issue involves the placement of function declarations in a control statement, which is disallowed in the ECMAScript spec, although it works in the browser. Finally, Microsoft won't support the "const" or constant function in IE 9 because it can generate errors in complex scenarios.

The blog claims that Microsoft uses its principled decision-making concepts in deciding whether or not to implement features in IE 9. For instance, the IE team assesses if the feature is considered to be "a consensus feature" of the Web developer community. They also consider if adopting the feature in IE 9 would help the standard or set it back.

IE 9 will have its public unveiling on Sept. 15, but Microsoft has been beating the standards drum for some time throughout IE 9's various "platform preview" releases over several months' time. The IE team wants to assure developers that IE 9, now available as "platform preview 4," won't repeat IE 6's history. IE 6 is typically viewed by developers as having deviated from standards in important ways.

Microsoft has billed IE 9 as being on the cusp of developing standards, including HTML 5, SVG 1.1, CSS 3 and others. The company contributed 2,138 tests to working groups to clear up ambiguities in those standards. However, when it comes to implementation, it all boils down to "a judgment call," according to Allen Wirfs-Brock, a Microsoft JavaScript language architect, writing in the IE blog post.

So far, Microsoft's Chakra engine in IE 9 has scored well on JavaScript tests. For instance, platform preview 4 of IE 9 had top WebKit SunSpider test results, as reported by Microsoft this month. However, IE 9's predecessor, IE 8, hasn't fared so well. IE 8 placed dead last for conformance with the ECMAScript 5 spec when Google tested it using its Sputnik conformance test suite, as reported by Google in March.